Benzo(a)pyrene, a polycyclic aromatic hydrocarbon, and potent reproductive toxin in rodents has been used to explore site and mechanism of action of ovarian toxicity. Benzo(a)pyrene is an indirect acting reproductive toxin destroying oocytes or follicles following metabolic processing to one or more reactive intermediates by ovarian or extra-ovarian enzyme systems. Intraovarian injection studies have demonstrated that the ovary has the full complement of enzymes necessary for metabolic activation of benzo(a)pyrene to toxic metabolites. Following intraperitoneal treatment murine differences in ovarian metabolic processing are not reflected in differences in ovarian toxicity, suggesting metabolic activation by extraovarian tissues such as the liver can contribute to ovarian toxicity. Intraovarian injection studies, and preliminary analysis of ovarian metabolism using the trans-7,8-dihydrodiol metabolite of benzo(a)pyrene as the substrate suggests that the rate limiting step in ovarian metabolic activation may be the recycling of the dihydrodiol to the diol-epoxide. Although the non-human primate appears less sensitive to ovarian toxicity than the mouse following intraperitoneal treatment, the ovary of the non-human primate is able to metabolize benzo(a)pyrene to dihydrodiols more efficiently than the mouse ovary.